The broad objectives of this research are to determine some of the mechanisms of in vivo control of blood coagulation and to provide information on the functions of the carbohydrate portion of the blood-clotting glycoproteins. In general, carbohydrate functions are mediated through "recognition", where the carbohydrate serves as a recognition site. These types of functions can be observed only in very complex system or in vivo which necessitates the development of elaborate procedures for their detection. Several recent literature reports present evidence that carbohydrate is important to blood coagulation at the level of platelet adhesion and aggregation and that it may also be important in fibrin formation. The recent observation that prothrombin, the "pro" form of the enzyme which is responsible for fibrin formation, contains the very unusual alpha-anomeric form of galactose raises the strong possibility that this alpha-galactose performs a specific function which may be inportant to blood-coagulation, possibly in a regulatory role. Further studies on the carbohydrate portion of other blood-clotting glycoproteins are also planned. In addition, another study is aimed at complete characterization of the vitamin K-dependent region of prothrombin. Vitamin K is required for the biosynthesis of the calcium-binding sites of prothrombin which are gamma-carboxyglutamic acid residues. The complete characterization of how these unusual amino acid residues are involved in calcium chelation are proposed.